Cellulosic structure and method of making the same



Oct. 18, 1938. F Q N BR 2,133,805

CELLULOSIC STRUCTURE AND METHOD OF MAKING THE SAME Filed Dec. 18, 1936EINVENTOR.

C'lulrfes 71.5mm: 7%

A TTORNEYS.

' Patented Oct. 18, 1938 warren STATES Charles N. Brown,

du Pont de Nemours CEILULOSIC STRUCTURE ANDMET HOD MAKING THE SAMEBufialo, N. Y 'assignor tell. I

& Company, W

Del., a corporation of Delaware Application December 18, 1936, SerialNo. 116,599

6 Claims.

This invention relates to artificial porous materials made fromcellulosic solutions such as viscose. More particularly, it relates toartificial cellulosic sponges having different characteristics indifierent parts thereof, such as different sizes of pores. The inventionwill be described in terms of the production of such masses from viscoseby mixing viscose with a pore-forming material and then coagulating andregenerating the same, followed by the removal of the poreformingmaterial. It is to be understood, however, that this is to be consideredas illustrative and not limitative. In the common method of formingporous articles such as artificial sponges from viscose, a certainquantity of viscose from green or unripened alkali cellulose is mixedwith a solid poreforming material such as sodium sulfate decahydrate,together with a suitable quantity of reinforcing material such as hemp,sisal, cotton or other fibrous material. The pore-forming materialsupplied may be of various sizes, according to the use to which thesponge is to beput. For example, in the washing of cars or other largeobjects subject to the roughening influences of dirt and weather, asponge with large size pores is desired. On the other hand, in thepolishing of silver or for photographic or other precision purposes, asponge with extremely fine pores is desired. For other purposes, it isoften desiredthat at one particular stage a fine pored sponge be usedand at another stage a coarse pored sponge be used or that both be usedsimultaneously. Up to the present time, in order to accomplish thisresult, it has been necessary to have a plurality of sponges on hand,with the resultant expenditure of time and eifort in changing from onesponge to another. On '00- casion, users of such sponges have been knownto sew or tie together sponge sections having different sized pores.Such an expedient is obviously imperfect. It secures union only atisolated points, tends to come apart upon merely slight usage, and ofcourse is only loose in nature.

In order to overcome these dimculties, it has been suggested to cementsections of sponges of 'dliferent sized pores by means of suitableadhesive compositions. This procedure is also subject to thedisadvantage that the so-united sponge sections tend to come apart uponhard usage, partly because adhesive contact in many cases is securedonly at meeting edges, or where an edge meets with a face, and partlybecause an adhesive joint is usually not as strong as the base materialswhich it unites. ;If a larger quan- 5 tity of adhesive substance isused, so that better adhesive union than would otherwise be obtained issecured, aninfiexible impervious layer is apt to be secured between thetwo porous layers of different pore size. This, for many p'urposesfw isobjectionable. Furthermore, the union obtained when a foreign substanceis used as the cementing agent cannot be as strong .as the spongestructure itself. Finally, the chemical nature of the adhesive used maybe such that 15 it has a harmful effect on the cellulosic structure, orbe detrimental to the articles on which the sponge is used.

It is therefore an object of this invention to produce artificial porousobjects of cellulosic ma- 20 terial having a plurality of differentcharacteristics in difierent sections thereof, called hereinafter acomposite sponge. It is afurther object to produce artificial cellulosicsponges having:

sections of diflerent pore fineness in different 25 parts thereof. It isa still further object to produce such sponges without the aforememtioned disadvantages. Other objects will appear hereinafter.

The-objects of this invention in general are accomplished by forming aplurality of cellulosic masses having pore-forming material therein,said-masses having different characteristics, such as difierent averageparticle size of the poreforming material, bringing said masses intojuxtaposition, and subsequently coagulating and/or regenerating, thecomposite mass thus formed.

In the drawing, Figure 1 illustrates a rectangular porous article orsponge in accordance with .this invention. Figure 2 shows a modifiedform 40 of sponge according to this invention. Figure 3 shows acylindricalsponge having a center portion of different average pore sizethan theperipheral portion.

In the practice of this invention, a plurality of different batches ofsponge forming material is made up in well known fashion. Forconvenience, the invention will be described in terms of the manufactureof'sponges having pores of two different'average sizes. Two portions ofa suitable viscose containing fibrous strengthening material such ashemp are separately and thoroughly mixed with a pore-forming'materialsuch as sodium sulfate decahydrate. In one portion the pore-formingmaterial may be of a size sufilcient to form pores comparable in size tothose occurring in natural sponges. In the second portion thepore-forming material may .be of such a size as toform pores ofconsiderably forming material from one portion is introduced a into arectangular mold and smoothed out into a uniform layer. A quantity ofsponge-forming material from the other portion is then superimposed uponthe first layer, and smoothed as before. The process may be repeated byalternating material from first one portion and then 'the other, or themass may be subjected to the following step after the introduction ofthe second layer. In any case, the mass is subjected to pressure for ashort period, in order to eliminate bubbles, etc. The mass is then readyfor coagulation and regeneration, which maybe accomplished in any of thewell known methods, such as by means of boiling salt solution, steam,

heating by means of electrical resistance, etc.

After being suitably washed, purified, and, if necessary, treated withother ingredients such as a'softener for example, glycerin, the spongemass is dried and cut up into a plurality of individual blocks. Theseblocks may be cut up in such a way that all'of the sponges formedtherefrom will have both fine and coarse pored material in the samesponge, or some of the individual blocks may contain only fine pores andothers only coarse pores. These-factors, of course, may be suitablyadjusted, according to the size of the sponge and the thickness of thelayers introduced into the mold. If it is desired to have a large numberof small size composite sponges, more than two layers may be introducedinto the mold. One of the sponges produced by this method is shown inFigure l of the drawing, in which 3 is the coarse pored part and l thefine pored part. As an alternative to the above procedure, the spongesmay be formed continuously and cut off into individual sponges andforced through a die into a heated tube. The die, for example, may beconcentrically divided so that fine pored material is forced through theinner portion and coarse pored material through the outer portion, orvice versa. Coagulation and regeneration is accomplished by heating thetube or by heating the mass by means of electrical resistance, so thatthe sponge mass emerges from the end thereof completely coagulated andregenerated. A sponge formed by this method is illustrated in Figure 8.

The bulky nature of the material operated upon renders it'necessary thatthe coagulation and regeneration of the mass occupy a considerableperiod of time, for example, 1 to 12 hours. It is therefore somewhatsurprising that during this period of time the separate portions ofsponge forming material do not intermingle, especially in the interior,where the coagulating and regenerating action is longest in takingeffect. It has been found, however, that due to the high viscosity ofthe masses, this intersharply defined.

minglingtakes place to a very slight extent only. and the lines ofdemarcation are therefore Example The following example illustrates onepreferred method for carrying out the invention. A sponge-forming massis made up of the following vmixture:

Pounds 20% cellulose viscose 160 Vegetable fiber Glaubers salt having anaverage particle size of millimeters in diameter 1200 A secondsponge-forming massis made up of the following mixture:

Pounds 20% viscose 160 Vegetable fib 16 Glaubers salt having an averageparticle size of 2 millimeters in diameter. 1200 A sufficient quantityof the first mass of spongeforming material is introduced into arectangular mold to form a layer one inch thick in the bottom thereof,and is then smoothed to a uniform thickness. A sufficient quantity ofthe .second mass of sponge-forming material is then introduced onto thetop of the first mass to form a layer an inch and half thick, andsmoothed as before. Additional layers alternately from the first andsecond masses are added until the mold is full. The composite mass isthen subjected to pressure for a short period, in order to remove airbubbles, etc. It is then introduced into a vat containing a hot orboiling solution of sodium sulfate in order to coagulate and regeneratethe mass. After a period of about 12 hours, it is withdrawn therefrom,washed with water, treated with acid, again washed with water, bleached,againwashed with water, impregnated with glycerin, and dried. Afterdrying, the sponge mass is cut up into a plurality of blocks similar toFigure 1' of the drawing. f

The invention has been described generally with reference to a porousarticle having pores of'two different average sizes. It is to beunderstood, of course, that the difference in character istics may beother than in pore size, such as color, strength, flexibility orsoftness, or any combination of these. For example, a red spongeformingmass having large pores might be united to a blue sponge-forming masshaving small pores. Furthermore, more than two spongeforming masses maybe united in this fashion, such 'as to form a red, white and bluesponge. Additionally, the separate batches may be imperfectly mixedbefore coagulation and regeneration whether the separate batches be-ofdifierent pore size or different color or other differentcharacteristics. For example, a sponge having mottled effects might beproduced by imperfectly mixing batches of difierent colors. Finally theline of division may not be approximately straight as in the aboveexample but may be curved or circular as in the modification shown inFigure 3. The line of division may extend along the long axis, as inFigure 1, or the short axis, as in Figure 2, of a rectangular sponge,according to the use to which it is put. For example, it may be desiredto use a sponge of fine and coarse pores in which both are usedsimultaneously over diflerent portions of the surface to be treated. Forexample,

if it is desired to rub a surface with a coarse pored sponge followed bya fine pored sponge, this could be done in a single operation by forcinga sponge as illustrated in Figure 2 across the surface with the coarseportion'being pushed in advance of the fine portion.

Such a sponge has many other uses. The,

coarse pored side, for example, could be used for washing an object andthe fine pored side for drying it by rubbing the sponge over the surfaceof theobject. A sponge having a plurality of pore sizes of successivelydiminishing size can be used as a composite filtering material so thatthe larger particles could be removed by the coarser-pored portion andthe smaller particles by the finer pored material without impeding the.passage of the liquid being filtered.

The invention has been described in terms of the making of porousobjects from viscose. It is to be understood, of course, that othercellu losic solutions are equally applicable 'such as lowly etherifiedand lowly esterified cellulose ethers and esters, for example, lowlyetherified glycol cellulose, lowly etherified methyl cellulose andothers.

Since it is obvious that various changes and modifications may be madein the above description without departing from the nature and spiritthereof, it is understood that the invention is not to be-limitedthereto except as set forth in the appended claims.

I claim:

1. An integral, absorbent, porous article of cellulosic material, saidarticle comprising two parts of different average pore sizes unitedalong a single meeting face.

2. An integral, absorbent, porous article of cellulose regenerated fromviscose, said article comprising two parts of different average poresize united along a single meeting face, said parts being formed bybringing into juxtaposition along.

a single meeting-face two viscoses containing solid pore-formingmaterials of different average particle sizes and .then coagulating andregenerating.

3. An integral, absorbent, porous article of cellulose regenerated fromviscose, comprising a first part havingpores of a relatively largeaverage size, and a second part having pores of a relatively smallaverage size, said parts united along a single meeting face and beingformed by bringing into juxtaposition along a single meeting face 50 amixture of fibrous strengthening material and viscose containing a solidpore-forming material having an average particle size of at least 6millimeters in diameter with a mixture of fibrous strengthening materialand viscose containing a pore-forming material having an averageparticle size of less than 4 millimeters in diameter, and coagulatingand regenerating the composite mass thus formed.

4. The method of forming absorbent, porous articles comprising forming amixture of a solid pore-forming material and a coagulable cellulosicsolution, forming a second mixture of a solid pore-forming material anda coagulable cellulosic solution, the pore-forming materials in said twomixtures having diiferent average particle sizes, bringing said mixturesinto juxtaposition along a single'me'eting face, coagulating saidmixtures into the form of a unitary. mass, purifying and drying saidmass, and sub-dividing said mass into a plurality of individual units,at least some of said units comprising porous material from both of saidmixtures.

5. The method of forming absorbent, porous earticles comprising forminga mixture of viscose and a solid pore-forming material, forming a sec--vond mixture of viscose and a solid pore-forming material of differentaverage particle size than said first mentioned pore-forming material,bringing said mixtures into juxtaposition along a single meeting face,coagulating and regenerating said mixtures into the form of a unitarymass, purifying and drying said mass, and sub-dividing said mass into aplurality of individual units, at

.least some of said units containing pores of both large and small size.

6. The method of forming absorbent, porous articles comprising forming amixture of viscose and a solid pore-forming material having an averageparticle size of less than 4 millimeters in diameter, forming a secondmixture of viscose and a solid pore-forming material having an CHARLESN. BROWN. '0

